Hypertrichosis is the excessive growth of hair on certain parts of the body (localized) or throughout the body (generalized). This excessive hair growth is either due to the increased length of the hair or greater density of hair on the affected area of the body. Hypertrichosis is not the same as hirsutism, where the hair growth on women is typical of male pattern hair growth on the body, due to androgens (male sex hormones).
In hypertrichosis, the excessive hair growth may be due to any type of hair including the lanugo, vellus or terminal hair type. Lanugo is the fine downy hair seen in newborns and usually shed within the first year of life. Vellus hair continues through childhood and increases in density after puberty. Vellus hair is also fine hair but thicker than lanugo and usually shorter and thinner than terminal hair. Terminal hair is the thick type of hair which occurs on the pubic region and axillae (armpits) of both men and women. Terminal hair may also occur on the mustache or beard area, chest, legs, hands and sometimes back of men.
Types and Causes of Excessive Body Hair Growth
Hypertrichosis is not usually related to any medical condition. It may be due to genetic factors, either familial or racial. Women of Mediterranean, Middle Eastern and Asian ethnic backgrounds usually have more body hair and this is considered a norm. There is no specific way to identify and diagnose what could be considered as hypertrichosis as the presentation may differ from person to person and may be dependent on race, sex and age. In men, hypertrichosis is not usually identifiable as dense hair growth is seen as the norm is the adult male.
Hypertrichosis may be congential (present at birth) or acquired (occurs later in life due to other diseases, conditions or drugs). The excessive hair growth may be localized or generalized. One of the most severe forms of hypertrichosis is seen in Wolfman’s syndrome or congenital hypertrichosis languinosa or congenital hypertrichosis terminalis. This is a rare condition due to genetic factors and only a few cases have been documented to date. The type of hair occurring in this condition is usually lanugo hair or terminal hair.
Nevoid hypertrichosis is the excessive growth of hair on dark, pigmented patches or spots on the body, as in a mole. These dark patches are usually raised and may result be the result of a birthmark or Becker nevus, vascular causes (spider nevus) or congenital melanocytic nevus (mole at birth).
Acquired hypertrichosis usually affects a specific area of the body and may be due to a number of metabolic or dermatological as well as certain substances. Drug induced hypertrichosis may occur as a result of oral medication (phenytoin, anabolic steroids, cyclosporin) or topical applications (corticosteroids, minoxidil, iodine). Oral medication may causes generalized acquired hypertrichosis. Other causes of acquired hypertrichosis include thyroid disorders, chronic skin inflammation (like lichen simplex) or metabolic disorders (porphyria cutanea tarda).
Malnutrition linked to eating disorders like anorexia nervosa or bulimia may also result in acquired hypertrichosis. Superficial skin damage or irritation may also result in hypertrichosis, like cuts (minor abrasions), skin infections, vaccinations and the use of plaster casts. In cases of systemic illnesses, like HIV/AIDS, hypertrichosis has been noticed, especially in the ears, eyelashes and eyebrows.
Treatment of Hypertrichosis
Treatment is similar to hirsutism and appropriate hair removal methods should be considered. These include shaving, waxing, electrolysis and the use of depilatory creams. Hair retarding agents like eflornithine may be considered or alternatively hair masking applications like bleach could be used. In cases of hypertrichosis due to drugs, metabolic or systemic illnesses, treatment should be directed at the cause although hypertrichosis should not be the sole reason for treating these underlying conditions.